use MIDI;
 use strict;
 use warnings;
 my @events = (
   ['text_event',0, 'MORE COWBELL'],
   ['set_tempo', 0, 450_000], # 1qn = .45 seconds
 );

 for (1 .. 20) {
   push @events,
     ['note_on' , 90,  9, 56, 127],
     ['note_off',  6,  9, 56, 127],
   ;
 }
 foreach my $delay (reverse(1..96)) {
   push @events,
     ['note_on' ,      0,  9, 56, 127],
     ['note_off', $delay,  9, 56, 127],
   ;
 }

 my $cowbell_track = MIDI::Track->new({ 'events' => \@events });
 my $opus = MIDI::Opus->new(
  { 'format' => 0, 'ticks' => 96, 'tracks' => [ $cowbell_track ] } );
 $opus->write_to_file( 'cowbell.mid' );